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    #1

    Need opinion: shorted motherboard or CPU?

    I built my latest computer with a Gigabyte B85-D3V motherboard and an Intel i3 G3220 CPU.
    It worked long enough for me to install windows 8.1 to my SSD
    but now when power button is pressed the PSU and CPU fans both run
    for about 2 seconds and then stop and then will then cycle again for 2 seconds.
    I am using this outside the case now with only CPU, memory and power supply connected. I have tried a different power supply and tried using only one memory chip so I am fairly certain it has to be either a bad motherboard or CPU.
    I removed the CPU and applied power and the PSU fan would cycle for 2 seconds. Does this indicate the motherbad is bad?
    I could return the CPU for factory warranty if I knew for sure it was bad.
    Is there any way to tell for certain which is defective? Also I am wondering
    if installing a good CPU in a shorted motherboard could ruin the CPU?
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    #2
    Re: Need opinion: shorted motherboard or CPU?

    was the contact area on the cpu clean?
    are the socket contacts o.k.?
    can you try a different cpu-fan?
    if the fan tacho signal is bad the mobo may think it's not running and shutdown.

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      #3
      Re: Need opinion: shorted motherboard or CPU?

      CPUs die very very rarely. If something's died, that must be the board. Power the board up with CPU but without the ATX12v connector plugged. If it turns on and stays on, you have a shorted VRM on the motherboard.
      Originally posted by PeteS in CA
      Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
      A working TV? How boring!

      Comment

        #4
        Re: Need opinion: shorted motherboard or CPU?

        Thanks for replies. Here's an update:
        Now when I push the power button neither the CPU fan or PSU fan moves UNLESS I remove the ATX 12v 8pin connector. Then the CPU and PSU have the 2 second cycle as before.
        The CPU socket is clean and contacts are good. I have tried a different CPU fan with same result.

        Comment

          #5
          Re: Need opinion: shorted motherboard or CPU?

          see if the pins are shorted together on the mobo 12v connector with a meter.

          Comment

            #6
            Re: Need opinion: shorted motherboard or CPU?

            Measured between the pins on the 12v connector I get very low ohm readings (from about 1 to 7 ohms) but not a complete short. Is this normal?

            Comment

              #7
              Re: Need opinion: shorted motherboard or CPU?

              No. You have a shorted mosfet in the VRM.
              Originally posted by PeteS in CA
              Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
              A working TV? How boring!

              Comment

                #8
                Re: Need opinion: shorted motherboard or CPU?

                I suspected the MB was bad, glad you could confirm it for me.
                So I plan on ordering a new MB (maybe not a gigabyte this time) but I am
                wondering in case the CPU is shorted too, could this ruin the new motherboard?

                Comment

                  #9
                  Re: Need opinion: shorted motherboard or CPU?

                  cpu is probably fine.

                  someone with hot air should be able to replace the shorted fet(s) on the dead board.

                  Comment

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